Sažetak
The charge transport in the copper-oxygen chain/ladder layers of \laysrca{; ; }; ; is investigated along two crystallographic directions in the temperature range from 50~K to 700~K and for doping levels from $y \approx 6$ (number of holes $n_h <1$) to $y = 0$ (number of holes $n_h = 6$). A crossover from a one-dimensional hopping transport along the chains for $y \geq 3$ to a quasi-two-dimensional charge conduction in the ladder planes for $y \lesssim 2$ is observed. This is attributed to a partial hole transfer from chains to ladders when the hole doping exceeds $n_h \approx 4$ and approaches fully doped value $n_h = 6$. For $y \lesssim 2$ a weak dielectric relaxation at radio-frequencies and a microwave mode are detected, which might be recognized as signatures of a charge-density wave phase developed at short length scales in the ladders planes.